METACARPAL CORTICAL THICKNESS BY COMPUTED RADIOGRAPHY IN OSTEOPOROSIS

Computed radiography was used to make radiogrammetric measurements of the second metacarpal in 240 women, 180 considered normal and 60 osteo porotic. These measurements had a coefficient of variation for the ext ernal diameter of 0.74% in normal women and 0.75% in osteoporotic wome n, and for the internal diameter of 2.4% and 2.03%, respectively. The group of women with osteoporosis was divided according to external dia meter and internal diameter into a group with osteoporosis due to incr eased bone resorption (61.1%, normal external diameter and increased i nternal diameter), and osteoporosis due to deficient bone formation (2 6.1%, decreased external diameter and normal internal diameter). In th e remaining subjects (12.8%), osteoporosis was attributed to both mech anisms. There was a significant linear regression between internal dia meter and tartrate-resistant acid phosphatase concentration (p < 0.000 1) in the group of increased bone resorption, which was absent (p = ns ) in the group with deficient bone mass formation. No changes were obs erved in the size of the two groups. The low coefficient of variation of radiogrammetric measurements with computed radiography validate it as an accurate technique for bone mass studies. Moreover, it has the a dditional advantage of permitting determination of the proportion of w omen with osteoporosis due to increased bone resorption and/or deficie nt bone mass formation.